Method for the detection of curves and the determination of the transverse acceleration in a vehicle

ABSTRACT

A method for detecting when a vehicle drives in a curve for which the wheel speed sensors of the non-driven wheels are sufficient and supplies a correct statement even in case of interferences or different circumferential distances. Also, an output signal can be recovered which corresponds to the values of the available transverse acceleration.

This application is a continuation of application Ser. No. 07/466,370, filed May 9, 1990, now abandoned.

BACKGROUND OF THE INVENTION

The invention relates to a method for generating different signals depending on whether a vehicle drives in a curve or on a straightaway and a method for determining the transverse acceleration while driving in curve.

From navigation systems it is known to determine the approximate driving direction of the vehicle from the difference Δv of the sensor signals from the non-driven wheels of a vehicle.

In anti brake lock control systems or anti slip control systems, it is also known to use steering angle sensors and/or transverse accelerometer and supply the output signals thereof as parameters to the control. The use of only the difference ΔV is not sufficient in this case since interferences can adversely affect these differences and since different circumferential distances (wheel diameters) can also lead to incorrect statements.

According to the invention, the difference Δv between the speeds of the left and right non-driven wheels is filtered so that the filtered difference Δv_(F) follows those changes having an increase greater than ± a with a delay, where a is about 0.2 g.

Δv_(F) and the mean valve v_(M) of the speed signals serve to form correction signals K_(i) according to the relation: ##EQU1## where Δv_(g) is a function which is stored and dependent upon the vehicle speed, and K₂ is formed only when |Δv_(F) |>Δv_(G). A mean value K_(i) is formed from the successively determined correction signals K_(i), and a corrected difference Δv_(k) is formed from Δv_(F) according to

    Δv.sub.K =Δv.sub.F -K.sub.i v.sub.M

wherein the correction K₁ is used when K₁ is formed once during a ride. A signal which indicates driving in a curve is generated if Δv_(K) exceeds a small speed value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of a preferred embodiment;

FIG. 2 illustrates a variation of the diagram of FIG. 1;

FIG. 3 is a plot of the differential speed signal Δv_(G) which is necessary to calculate the low speed correction signal, versus speed;

FIG. 4 is a plot of the corrected differential signal Δv_(K) for different transverse accelerations, versus speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 the sensors associated with the non-driven wheels bear the reference numerals 1 and 2 and the filters downstream thereof are referenced as 3 and 4. These filters are configured such that the output signals V_(LF) and V_(RF) of these filters can follow the wheel speed signals V_(L) and V_(R) of the sensors 1 and 2 only up to a maximum slope C of ±1.38 g, for example. A block 5 forms the difference ΔV of the filtered signals. A block 6 forms the average value of the filtered signals ##EQU2## A block 7 serves to filter the differential signal ΔV.

The filtering is configured such that the output signal ΔV_(F) of the filter 7 can follow the input signals ΔV only up to a maximum slope of for example ±0.18 g. This measurement is based on the knowledge that faster changes of interferences cannot be caused by normal speed changes.

A correction signal K₁ is formed in the blocks 8 and 9. For this purpose, the signals ΔV_(F) and V_(M) are supplied to block 8. Moreover, the threshold value stage 9 activates this block 8 only if the speed V_(M) (=vehicle speed) exceeds 100 km/h, for example. From the K₁ -values which are determined in successive, short periods of time, a block 10 forms the mean value K₁ which is then stored. At the twenty-first measurement, for example, the K₁ -value reads: ##EQU3## It is also possible to interrupt the mean value formation after a certain number of values and use only the last determined mean value while driving.

The blocks 11-13 are used to determine the correction values K₂. For this purpose, the signals ΔV_(F) and V_(M) are supplied to the subtracting block, the dividing block, and the comparing block 12.

The expression ##EQU4## is formed when the threshold value stage 11 activates the block 12 at V_(M) ≦100 Km/h and when ΔV_(F) >ΔV_(G). The value ΔV_(G) which is necessary for the formation of K₂ and the comparison is stored as a curve in memory 13. In FIG. 3, this curve ΔV_(G) is represented as a function of the speed V_(M). The area with the hatching, which the curve defines, represents the plausibility area. The curve itself represents the plansibility boundary speed in dependency upon the vehicle speed. Different circumferential distances (wheel diameters) or a rotation of the vehicle around the vertical axis can cause the value of (±ΔV_(F)) to exceed this limit. With an increasing speed, the plausibility check which is carried out in the invention gains effectiveness. Therefore, the correction value K₁ recovered above 100 km/h and when recovered even once, is preferred. A selector circuit 15 represented as a switch selects the value K₁ for the remainder of the ride if this value was recovered once while driving. This is indicated by line 15a. From the K₂ -values an averaged value K₂ is also recovered in a block 14.

In an overlaying block 16, the so recovered correction value K₁ or K₂, combined with V_(M), is overlayed on ΔV_(F) to form the corrected differential speed signal ΔV_(K) which is positive or negative depending on the curve direction. A downstream comparator 17 releases a signal when ΔV_(K) exceeds a small speed value of, for example, 2 km/h (curve determination) and changes the signal when, for example, the value falls below 1.5 km/h (straightaway determination).

If an element 18 where the curves corresponding to FIG. 4 are stored, where these curves represent the functions ΔV_(K) of speed for different transverse accelerations a_(q), is placed downstream of the overlaying element 16 of FIG. 2, it is possible to determine at this point the corresponding transverse acceleration a_(q) when inputting ΔV_(K) and the speed V_(M). The value can be output at terminal 19. 

We claim:
 1. Method for controlling one of brake slippage and drive slippage in a vehicle having two non-driven wheels when said vehicle is driven in a curve, said method comprisingmeasuring the speeds of said non-driven wheels to produce wheel speed signals V_(L) and V_(R) ; determining the difference ΔV=V_(L) -V_(R), said difference having a slope; filtering said difference to produce a filtered difference ΔV_(F) =ΔV when said slope is less than a predetermined value ± a, said filtered difference ΔV_(F) having a slope ± a when the slope of ΔV is greater than ±a; forming a mean value V_(M) =1/2(V_(L) +V_(R)); forming correction signals K_(i) according to the equations K₁ =ΔV_(F) /V_(M) when V_(M) exceeds a predetermined speed and K₂ =(ΔV_(F) -ΔV_(G))/V_(M) when V_(M) is less than or equal to said predetermined speed, ΔV_(G) being a stored value dependent upon vehicle speed, forming a mean value K_(i) from successively determined correction signals K_(i) ; forming a corrected speed difference ΔV_(K) =ΔV_(F) -K_(i) V_(M), wherein K_(i) =K₁ when K₁ was formed at least once during a ride, generating a signal indicative of a curve when ΔV_(K) exceeds a curve determination speed value, and controlling one of brake slippage and drive slippage in said vehicle by using said signal indicative of a curve as a control parameter in a respective one of an antilock brake system and an antislip drive system of the vehicle.
 2. Method as in claim 1 wherein said predetermined value ± a is ±0.2 g.
 3. Method as in claim 1 wherein said curve determination value is 2 km/h.
 4. Method as in claim 3 wherein said straightaway determination value is 1.5 km/h.
 5. Method as in claim 1 further comprising generating a signal indicative of a straightaway when ΔV_(K) falls below a straightaway determination value.
 6. Method as in claim 1 wherein said predetermined speed is 100 km/h.
 7. Method as in claim 1 wherein said wheel speed signals V_(L) and V_(R) are filtered to produce respective filtered values V_(LF) and V_(RF) having a slope up to a predetermined value c.
 8. Method as in claim 7 wherein said predetermined value c is 1.4 g.
 9. Method for controlling at least one of brake slippage and drive slippage in a vehicle having two non-driven wheels when said vehicle is driven in a curve, said method comprisingmeasuring the speeds of said non-driven wheels to produce wheel speed signals V_(L) and V_(R) ; determining the difference ΔV=V_(L) -V_(R), said difference having a slope; filtering said difference to produce a filtered difference ΔV_(F) =ΔV when said slope is less than a predetermined value said filtered difference ΔV_(F) having a slope ± a; forming a mean value V_(M) =1/2(V_(L) +V_(R)); forming correction signals K_(i) according to the equations K₁ =ΔV_(F) /V_(M) exceeds a predetermined speed and K₂ =(ΔV_(F) -ΔV_(G))/V_(M) when V_(M) is less than or equal to said predetermined speed, ΔV_(G) being a stored value dependent upon vehicle speed, forming a mean value K_(i) from successively determined correction signals K_(i) ; forming a corrected speed difference ΔV_(K) =ΔV_(F) -K_(i) V_(M), wherein K_(i) =K₁ when K₁ was formed at least once during a ride, determining a transverse vehicle acceleration a_(q) by inputting said corrected speed value ΔV_(K) and said mean value V_(M) into a unit which stores plots of ΔV_(K) versus V_(M) for various transverse vehicle accelerations, and controlling one of brake slippage and drive slippage in said vehicle by using said transverse acceleration as a control parameter in a respective one of an antilock brake system and an antislip drive system of the vehicle.
 10. Method as in claim 9 wherein said predetermined value ± a is ±0.2 g.
 11. Method as in claim 9 wherein said predetermined speed is 100 km/h.
 12. Method as in claim 9 wherein said wheel speed signals V_(L) and V_(R) are filtered to produce respective filtered values V_(LF) and V_(RF) having a slope up to a predetermined value c.
 13. Method as in claim 12 wherein said predetermined value c is ±1.4 g. 